Americium and Curium Chemistry

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15 Νοε 2013 (πριν από 3 χρόνια και 10 μήνες)

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15
-
1

Americium and Curium
Chemistry


From: Chemistry of actinides


Nuclear properties


Production of Am isotopes


Am separation and purification


Metallic
state


Compounds


Solution chemistry


Coordination chemistry


Analytical Chemistry

15
-
2

Production of Am isotopes


Am first produced from neutron irradiation of
Pu


239
Pu to
240
Pu to
241
Pu, then beta decay of
241
Pu


241,243
Am
main isotopes of interest


Long half
-
lives


Produced in kilogram quantity


Chemical studies


Both isotopes produced in reactor


241
Am


source for low energy gamma and alpha


Alpha energy 5.44
MeV

and 5.49
MeV


Smoke detectors


Neutron sources


(
a
,n
) on Be


Thickness gauging and density


242
Cm production from thermal neutron
capture


243
Am


Irradiation of
242
Pu, beta decay of
243
Pu


Critical mass


242
Am in solution


23 g
at
5 g/L


Requires isotopic separation

15
-
3

Am solution chemistry


Oxidation states III
-
VI in solution


Am(III,V) stable in dilute acid


Am(V, VI)
form
dioxo

cations


Am(II)


Unstable, unlike some lanthanides (
Yb
,
Eu
,
Sm
)


Formed from pulse radiolysis

*
Absorbance at 313 nm

*
T
1/2
of oxidation state 5E
-
6 seconds


Am(III)


Easy to prepare (metal dissolved in acid, AmO
2

dissolution)


Pink in mineral acids, yellow in HClO
4

when Am is 0.1 M


Am(IV)


Requires
complexation

to stabilize


dissolving Am(OH)
4

in NH
4
F


Phosphoric or pyrophosphate (P
2
O
7
4
-
) solution with anodic
oxidation


Ag
3
PO
4

and (NH
4
)
4
S
2
O
8


Carbonate solution with electrolytic oxidation


15
-
4

Am solution chemistry


Am(V)


Oxidation of Am(III) in near neutral solution


Ozone, hypochlorate (ClO
-
), peroxydisulfate


Reduction of Am(VI) with bromide


Am(VI)


Oxidation of Am(III) with S
2
O
8
2
-

or Ag
2+

in dilute non
-
reducing acid (i.e., sulfuric)


Ce(IV) oxidizes IV to VI, but not III to VI completely


2 M carbonate and ozone or oxidation at 1.3 V


Am(VII)


3
-
4 M NaOH, mM Am(VI) near 0
°
C


Gamma irradiation 3 M NaOH with N
2
O or S
2
O
8
2
-

saturated
solution

15
-
5

Am solution chemistry


Am(III) has 9 inner sphere waters


Others have calculated 11 and 10 (XAFS)


Based on fluorescence spectroscopy


Lifetime related to coordination

*
n
H2O
=(x/
t
)
-
y


x=2.56E
-
7 s, y=1.43


Measurement of fluorescence lifetime in H
2
O

and
D
2
O


15
-
6

Am solution chemistry


Thermodynamic data available (NEA data)


Systematic differences at Am


Thermodynamic changes with atomic number


Deviation at Am due to positive entropy of vaporization

15
-
7

Am solution chemistry


Autoreduction


Formation of H
2
O
2

and HO
2

radicals from
radiation reduces Am to trivalent states


Difference between
241
Am and
243
Am


Rate decreases with increase acid for
perchloric

and sulfuric


Some disagreement role of Am concentration


Concentration of Am total or oxidation state


Rates of reduction dependent upon


Acid, acid concentration,


mechanism

*

Am(VI) to Am(III) can go stepwise


starting ion

*
Am(V) slower than Am(VI)

15
-
8

Am solution chemistry


Disproportionation


Am(IV)


In nitric and
perchloric

acid


Second order with Am(IV)

*
2 Am(IV)

䅭⡉䥉⤠⬠䅭⡖)

*
Am(IV) + Am(V)

䅭⡉䥉⤠⬠䅭⡖䤩


Am(VI) increases with sulfate


Am(V)


3
-
8 M HClO
4

and
HCl

*
3 Am(V) + 4 H
+

Am(III)+2Am(VI)+2 H
2
O


Solution can impact oxidation state stability

15
-
9

Am solution
chemistry:
Redox

Kinetics


Am(III
) oxidation by
peroxydisulfate


Oxidation due to thermal
decomposition products


SO
4
.
-
, HS
2
O
8
-


Oxidation to Am(VI)


0.1 M to 10
nM

Am(III)


Acid above 0.3 M limits oxidation


Decomposition of S
2
O
8
2
-


Induction period followed by reduction


Rates dependent upon temperature,
[HNO
3
], [S
2
O
8
2
-
], and [
Ag
+2
]


3/2 S
2
O
8
2
-

+ Am
3+
+2 H
2
O

3 SO
4
2
-

+AmO
2
2+
+4H
+


Evaluation of rate constants can
yield 4 due to
peroxydisulfate

decomposition


In carbonate proceeds through Am(V)


Rate to Am(V) is proportional to
oxidant


Am(V) to
Am(VI)

*
Proportional to total Am and
oxidant

*
Inversely proportional to
K
2
CO
3


15
-
10

Am solution chemistry: Redox kinetics


Am(VI) reduction


H
2
O
2

in
perchlorate

is 1
st

order for peroxide and Am


2 AmO
2
2+
+H
2
O
2

2 AmO
2
+

+ 2 H
+
+ O
2


NpO
2
+


1
st

order with Am(VI) and
Np
(V)

*
k=2.45E4 L / mol s


Oxalic acid reduces to equal molar Am(III) and Am(V)


Am(V) reduction


Reduced to Am(III) in
NaOH

solutions


Slow reduction with dithionite (Na
2
S
2
O
4
), sulfite (SO
3
2
-
),
or
thiourea

dioxide ((NH
2
)
2
CSO
2
)



Np
(IV) and
Np
(V)


In both acidic and carbonate conditions

*
For
Np
(IV) reaction products either
Np
(V) or
Np
(VI)


Depends upon initial relative concentration of
Am and
Np


U(IV) examined in carbonate

15
-
11

Am solution chemistry


Radiolysis


From alpha decay


1 mg
241
Am release 7E14 eV/s


Reduction of higher valent Am related to
dose and electrolyte concentration


In nitric acid need to include role of HNO
2


In perchlorate numerous species produced


Cl
2
, ClO
2
, or Cl
-

15
-
12

Am solution chemistry


Complexation

chemistry


Primarily for Am(III)


F
-
>H
2
PO
4
-
>SCN
-
>NO
3
-
>
Cl
-
>ClO
4
-


Hard acid reactions


Electrostatic interactions

*
Inner sphere and outer sphere


Outer sphere for weaker
ligands


Stabilities similar to trivalent lanthanides


Some enhanced stability due to participation of
5f electron in bonding

15
-
13

Am solution chemistry: Organics


Number of complexes examined


Mainly for Am(III)


Stability of complex decreases with
increasing number of carbon atoms


With
aminopolycarboxylic

acids,
complexation

constant increases
with
ligand

coordination


Natural organic acid


Number of measurements
conducted


Measured by spectroscopy and
ion exchange


TPEN (
N,N,N’,N’
-
tetrakis
(2
-
pyridylmethyl)
ethyleneamine
)


0.1 M NaClO
4
,
complexation

constant for Am 2 orders
greater than
Sm

15
-
14

Am(IV) solution chemistry


Am(IV) can be stabilized by
heteropolyanions


P
2
W
17
O
61

anion; formation of 1,1 and 1,2 complex


Examined by absorbance at 789 nm and 560 nm


Autoradiolytic

reduction

*
Independent of complex formation


Displacement by addition of
Th
(IV)

*
Disproportionation

of Am(IV) to Am(III) and
Am(VI)


EXAFS used with AmP
5
W
30
O
110
12
-


Cation
-
cation

interaction


Am(V)
-
U(VI) interaction in
perchlorate


Am(V) spectroscopic shift from 716
-
733 nm to 765 nm

15
-
15

Am separation and purification


Pyrochemical

process


Am from
Pu


O
2

in molten salt, PuO
2

forms and precipitates


Partitioning of Am between liquid Bi or Al and molten
salts

*
K
d

of 2 for Al system


Separation of Am from PuF
4

in salt by addition of OF
2

*
Formation of PuF
6


Precipitation method


Formation of insoluble Am species


AmF
3
, K
8
Am
2
(SO
4
)
7

, Am
2
(C
2
O
4
)
3
,
K
3
AmO
2
(CO
3
)
2

*
Am(V) carbonate useful for separation from Cm

*
Am from lanthanides by oxalate precipitation


Slow hydrolysis of
dimethyloxalate


Oxalate precipitate enriched in Am


50 % lanthanide rejection, 4 % Am


Oxidation of Am(VI) by K
2
S
2
O
8

and precipitation of Cm(III)

15
-
16

Am solvent extraction


Am from lanthanides


HDEHP extract lanthanides better than actinides


Harder metal
-
ligand interaction


Basis of TALSPEAK


Preferential removal of actinides by contact with DTPA
solution

*
Reverse
-
TALSPEAK

*
Also useful with DIDPA


Selective actinide extraction with DTPA and 0.4 M NaNO
3

*
Ce/Am D
f

of 72


Recent efforts based on soft donor molecules


Sulfur and nitrogen containing ligands


Tripyridyltriazene (TPTZ) (C
5
H
4
N: pyridyl, (R
-
N:, azene)
and dinonylnapthalene sulfonic acid (HDNNS) in CCl
4

and dilute nitric acid

*
Preferential extraction of Am from trivalent
lanthanides

15
-
17

Am solvent extraction


Am from lanthanides


Initial work effected direction of further research


Focus on nitrogen and sulfur containing
ligands

*
Thione (Phosphine SO), pyridenes,
thiophosphonic acid


Research does not follow CHON principles


Efforts with Cyanex 301 achieved
lanthanide/actinide separation in pH 3 solution


Bis (2,4,4
-
trimethylpentyl)dithiophosphinic
acid

15
-
18

Am solvent extraction


Lanthanide/actinide separation


Extraction reaction


Am
3+
+2(HA)
2

AmA
3
HA+3 H
+

*
Release of protons upon complexation requires pH
adjustment to achieve extraction


Maintain pH greater than 3


Cyanex 301 stable in acid


HCl, H
2
SO
4
, HNO
3

*
Below 2 M


Irradiation produces acids and phosphorus compounds


Problematic extractions when dosed 10
4

to 10
5
gray


New dithiophosphinic acid less sensitive to acid concentration


R
2
PSSH; R=C
6
H
5
, ClC
6
H
4
, FC
6
H
4
, CH
3
C
6
H
4


*
Only synergistic extractions with, TBP, TOPO, or
tributylphosphine oxide

*
Aqueous phase 0.1
-
1 M HNO
3

*
Increased radiation resistance

15
-
19

15
-
20

Ion exchange


Cation exchange


Am
3+

sorbs to cation exchange resin in dilute acid


Elution with
a
-
桹摲潸祬楳潢畴祲慴攠慮搠
慭楮a灯汹捡牢潸祬楣 慣楤a


Anion exchange


Sorption to resin from thiocyanate, chloride, and to a limited
degree nitrate solutions


Inorganic exchangers


Zirconium phosphate


Trivalents sorb

*
Oxidation of Am to AmO
2
+

achieves separation


TiSb (titanium antimonate)


Am
3+

sorption in HNO
3


Adjustment of aqueous phase to achieve separation

15
-
21

Ion exchange separation Am from Cm


Separation of tracer level Am and Cm has been performed with displacement
complexing chromatography


separations were examined with DTPA and nitrilotriacetic acid in the
presence of Cd and Zn as competing cations



use of Cd and nitrilotriacetic acid separated trace levels of Am from Cm


displacement complexing chromatography method is too cumbersome to use
on a large scale


Ion exchange has been used to separate trace levels of Cm from Am


Am, Cm, and lanthanides were sorbed to a cation exchange resin at pH 2


separation was achieved by adjusting pH and organic complexant


Separation of Cm from Am was performed with 0.01 %
ethylenediamine
-
tetramethylphosphonic acid at pH 3.4 in 0.1 M
NaNO
3

with a separation factor of 1.4


Separation of gram scale quantities of Am and Cm has been achieved by cation and
anion exchange


methods rely upon use of
a
-
桹摲dxy汩獯扵瑹牡瑥to爠
摩整桹汥湥瑲楡m楮数敮瑡t捥t楣ia捩搠a猠s渠敬畴楮i ag敮琠o爠愠ra物r瑩潮to映瑨攠
敬畡湴n捯m灯獩瑩s渠批⁴桥ha摤楴楯d o映m整桡湯氠瑯t湩瑲楣na捩c


best separations were achieved under high pressure conditions


repeating the procedure separation factors greater than 400 were
obtained

15
-
22

Extraction chromatography


Mobile liquid phase and stationary liquid phase


Apply results from solvent extraction


HDEHP, Aliquat 336, CMPO

*
Basis for Eichrom resins

*
Limited use for solutions with fluoride, oxalate, or
phosphate


DIPEX resin

*
Bis(2
-
ethylhexylmethanediphosphonic acid on inert support

*
Lipophilic molecule


Extraction of 3+, 4+, and 6+ actinides

*
Strongly binds metal ions


Need to remove organics from support


Variation of support


Silica for covalent bonding


Functional organics on coated ferromagnetic particles

*
Magnetic separation after sorption


15
-
23

Am metal and alloys


Preparation of Am metal


Reduction of AmF
3

with Ba or Li


Reduction of AmO
2

with La


Bomb reduction of AmF
3

with Ca


Decomposition of Pt
5
Am


1550
°
C at 10
-
6

torr


La or Th reduction of AmO
2

with distillation of Am


Metal properties


Ductile, non
-
magnetic


Double hexagonal closed packed (dhcp) and fcc


Evidence of three phase between room temperature and melting point at 1170
°
C


Alpha phase up to 658
°
C


Beta phase from 793
°
C to 1004
°
C


Gamma above 1050
°
C


Some debate in literature


Evidence of dhcp to fcc at 771
°
C


Interests in metal properties due to 5f electron behavior


Delocalization under pressure


Different crystal structures

*
Conversion of dhcp to fcc


Discrepancies between different experiments and theory

15
-
24

Am metal, alloys, and compounds


Alloys investigated with 23 different
elements


Phase diagrams available for
Np
,
Pu
,
and U alloys


Am compounds


Oxides and hydroxides


AmO
, Am
2
O
3
, AmO
2

*
Non
-
stoichiometric

phases between Am
2
O
3

and AmO
2


AmO

lattice parameters
varied in experiments

*
4.95 Å and 5.045 Å

*
Difficulty in stabilizing
divalent Am


Am
2
O
3

*
Prepared in H
2

at 600
°
C

*
Oxidizes in air

*
Phase transitions with
temperature


bcc to
monoclinic
between 460
°
C
and 650
°
C


Monoclinic to
hexagonal
between 800
°
C
and 900
°
C

15
-
25

Am compounds


Am oxides and hydroxides


AmO
2


Heating Am hydroxides, carbonates, oxalates, or nitrates in air
or O
2

from 600
°
C to 800
°
C


fcc lattice

*
Expands due to radiation damage


Higher oxidation states can be stabilized


Cs
2
AmO
4

and Ba
3
AmO
6


Am hydroxide


Isostructural with Nd hydroxides


Cystalline Am(OH)
3

can be formed, but becomes amorphous due
to radiation damage

*
Complete degradation in 5 months for
241
Am hydroxide


Am(OH)
3
+3H
+
,

Am
3+
+3H
2
O

*
logK=15.2 for crystalline

*
Log K=17.0 for amorphous


Am hydrolysis (from CHESS database)


Am
3+
+H
2
O

䅭佈
2+
+H
+
: log K =
-
6.402


Am
3+
+2H
2
O

䅭⡏䠩
2
+
+2H
+
: log K =
-
14.11


Am
3+
+3H
2
O

䅭⡏䠩
3
+3H
+
: log K =
-
25.72


15
-
26

Solution absorption spectroscopy


Am(III)


7
F
0

5
L
6

at 503.2 nm (
e
=410 L mol cm
-
1
)


Shifts in band position and molar absorbance indicates changes in water or
ligand coordination


Solution spectroscopy compared to Am doped in crystals


Absorbance measured in acids and carbonate

15
-
27

Solution absorption spectroscopy


Am(IV)


In acidic media, broad absorption bands


13 M HF, 12 M KF, 12 M H
3
PO
4


Resembles solid AmF
4

spectrum

15
-
28

Solution absorption spectroscopy


Am(V)


5
I
4

3
G
5
; 513.7 nm; 45 L mol cm
-
1


5
I
4

3
I
7
; 716.7 nm; 60 L mol cm
-
1


Collected in acid, NaCl, and carbonate

15
-
29

Solution absorption spectroscopy


Am(VI)


996 nm; 100 L mol cm
-
1


Smaller absorbance at 666 nm


Comparable to position in Am(V)


Based on comparison with uranyl, permits analysis based on uranyl core with addition of electrons

15
-
30

Solution absorption spectroscopy


Am(VII)


Broad absorbance at 740 nm


Am(III) luminescence


7
F
0

5
L
6

at 503 nm


Then conversion to other excited state


Emission to
7
F
J


5
D
1

7
F
1

at 685 nm


5
D
1

7
F
2

at 836 nm


Lifetime for aquo ion is 20 ns


155 ns in D
2
O


Emission and lifetime changes with speciation


Am triscarbonate lifetime = 34.5 ns, emission at 693 nm


15
-
31

15
-
32

Am spectroscopy


Vibrational


AmO
2
+


Antisymmetric vibration in solids at 802 cm
-
1


Raman of Am(III) phosphate


Symmetric stretch of PO
4
3
-

at 973 cm
-
1


PO
3
-

groups at 1195 cm
-
1


X
-
ray absorption


Absorption edge at 18504 eV


4 eV difference between Am(IV) and Am(III)


15
-
33

Cm nuclear properties


Isotopes from mass 237 to 251


Three isotopes available in quantity for chemical
studies


242
Cm, t
1/2
=163 d

*
122 W/g

*
Grams of the oxide glows

*
Low flux of
241
Am target decrease fission of
242
Am, increase yield of
242
Cm


244
Cm, t
1/2
=18.1 a

*
2.8 W/g


248
Cm, t
1/2
= 3.48E5 a

*
8.39% SF yield

*
Limits quantities to 10
-
20 mg

*
Target for production of transactinide
elements

15
-
34

Cm Production


From successive neutron capture of higher Pu isotopes


242
Pu+n

243
Pu (
b
-
, 4.95 h)

243
Am+n

244
Am
(
b
-
, 10.1 h)

244
Cm


Favors production of
244,246,248
Cm


Isotopes above
244
Cm to
247
Cm

are not isotopically pure


Pure
248
Cm available from alpha decay of
252
Cf


Large campaign to product Cm from kilos of Pu


244
Cm separation


Dissolve target in HNO
3

and remove Pu by solvent extraction


Am/Cm chlorides extracted with tertiary amines from 11 M LiCl
in weak acid


Back extracted into 7 M HCl


Am oxidation and precipitation of Am(V) carbonate


Other methods for Cm purification included NaOH, HDEHP, and
EDTA


Discussed for Am

15
-
35

Cm aqueous chemistry


Trivalent Cm


242
Cm at 1g/L will boil


9 coordinating H
2
O from fluorescence


Decreases above 5 M HCl


7 waters at 11 M HCl


In HNO
3

steady decrease from 0 to 13 M


5 waters at 13 M


Stronger complexation with NO
3
-


Inorganic complexes similar to data for Am


Many constants determined by TRLFS


Hydrolysis constants (Cm
3+
+H
2
O

䍭佈
2+
+H
+
)


K
11
=1.2E
-
6


Evaluated under different ionic strength

15
-
36

15
-
37

Cm atomic and spectroscopic data


5f
7

has enhanced stability


Half filled orbital


Large oxidation potential for
III




Cm(IV) is
metastable


Cm(III) absorbance


Weak absorption in near
-
violet
region


Solution absorbance shifted 20
-
30 Å
compared to solid


Reduction of intensity in solid
due to high symmetry

*
f
-
f transitions are symmetry
forbidden


Spin
-
orbit coupling acts to reduce
transition energies when compared
to lanthanides


Cm(IV) absorbance


Prepared from dissolution of CmF
4


CmF
3

under strong fluorination
conditions

15
-
38

Atomic and spectroscopic data


Cm fluorescence


Fluoresce from 595
-
613 nm


Attributed to
6
D
7/2

8
S
7/2

transition


Energy dependent upon coordination
environment

*
Speciation

*
Hydration

*

complexation constants



15
-
39



0
10
20
30
Wavenumber (10
3
cm
-1
)
Absorption and fluorescence process of Cm
3
+

Optical Spectra

H

G

F

7/2

A

Z

7/2

Fluorescence Process

Excitation

Emissionless

Relaxation

Fluorescence

Emission

15
-
40

15
-
41

15
-
42

Cm separation and purification


Solvent extraction


Fundamentally the same as Am


Organic phosphates


Function of ligand structure

*
Mixed with 6 to 8 carbon chain better than TBP


HDEHP


From HNO
3

and LiCl

*
Use of membrane can result in Am/Cm separation


CMPO


Oxidation state based removal with different stripping
agent


Extraction of Cm from carbonate and hydroxide solutions,
need to keep metal ions in solution


Organics with quaternary ammonium bases, primary
amines, alkylpyrocatechols,
b
-
diketones, phenols


15
-
43

Cm separations


Ion exchange (similar to Am conditions)


Anion exchange with HCl, LiCl, and HNO
3


Includes aqueous/alcohol mixtures


Formation of CmCl
4
-

at 14 M LiCl

*
From fluorescence spectroscopy


TEVA resins


Same range of organic phases


Precipitation


Separation from higher valent Am


10 g/L solution in base


Precipitation of K
5
AmO
2
(CO
3
)
3

at 85
°
C


Precipitation of Cm with hydroxide, oxalate, or fluoride

15
-
44

Cm metallic state


Melting point 1345
°
C


Higher than lighter actinides Np
-
Am


Similar to Gd (1312
°
C)


Two states


Double hexagonal close
-
packed (dhcp)


Neutron diffraction down to 5 K


No structure change


fcc at higher temperature


XRD studies on
248
Cm


Magnetic susceptibility studies


Antiferrimagnetic transition near 65 K


200 K for fcc phase


Metal susceptible to corrosion due to self heating


Formation of oxide on surface

15
-
45

Cm metallic state


Preparation of Cm metal


CmF
3

reduction with
Ba

or Li


Dry, O
2

free, and above 1600 K


Reduction of CmO
2

with Mg
-
Zn alloy in MgF
2
/MgCl
2


Alloys


Cm
-
Pu

phase diagram studied


Noble metal compounds


CmO
2

and H
2

heated to 1500 K in Pt,
Ir
, or
Rh

*
Pt
5
Cm, Pt
2
Cm, Ir
2
Cm, Pd
3
Cm, Rh
3
Cm

15
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46

Cm
oxide compounds


Cm
2
O
3


Thermal decomposition of CmO
2

at 600
°
C and 10
-
4

torr


Mn
2
O
3

type cubic lattice


Transforms to hexagonal structure due to radiation
damage


Monoclinic at 800
°
C


CmO
2


Heating in air, thermal treatment of Cm loaded resin, heating
Cm
2
O
3

at 600
°
C under O
2
, heating of Cm oxalate


Shown to form in O
2
as low as 400
°
C


Evidence of CmO
1.95

at lower temperature


fcc

structure


Magnetic data indicates paramagnetic moment attributed to
Cm(III)


Need to re
-
evaluate electronic ground state in
oxides


Oxides


Similar to oxides of
Pu
, Pr, and Tb


Basis of phase diagram


BaCmO
3

and Cm
2
CuO
4


Based on high T superconductors


Cm compounds do not conduct


15
-
47

Cm compounds


Cm(OH)
3


From aqueous solution, crystallized by aging in water


Same structure as La(OH)
3
; hexagonal


Cm
2
(C
2
O
4
)
3
.
10H
2
O


From aqueous solution


Stepwise dehydration when heated under He


Anhydrous at 280
°
C


Converts to carbonate above 360
°
C

*
TGA analysis showed release of water (starting at 145
°
C)


Converts to Cm
2
O
3

above 500
°
C’


Cm(NO
3
)
3


Evaporation of Cm in nitric acid


From TGA, decomposition same under O
2

and He


Dehydration up 180
°
C, melting at 400
°
C


Final product CmO
2


Oxidation of Cm during decomposition

15
-
48

Review


Production and purification of Am and Cm isotopes


Suitable reactions


Basis of separations from other actinides


Formation of Am and Cm metallic state and properties


Number of phases, melting points


Compounds


Range of compounds, limitations on data


Solution chemistry


Oxidation states


Coordination chemistry


Organic chemistry reactions

15
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49

Questions


Which Cm isotopes are available for chemical
studies?


Describe the fluorescence process for Cm


What is a good excitation wavelength?


What methods can be use to separate Cm from
Am?


How many states does Cm metal have? What
is its melting point?


What are the binary oxides of Cm? Which will
form upon heating in normal atmosphere?

15
-
50

Questions


What is the longest lived isotope of Am?


Which Am isotope has the highest neutron induced
fission cross section?


What are 3
ligands

used in the separation of Am?


What are the solution conditions?


What column methods are useful for separating Am
from the lanthanides?


Which compounds can be made by elemental reactions
with Am?


What Am coordination compounds have been
produced?


What is the absorbance spectra of Am for the different
oxidation states?


How can Am
be detected?

15
-
51

Pop Quiz


How can high
valent

oxidation states of Am be
made?


Why does Cm have fewer accessible oxidation
states than Am?